MFI Fuel Fumes

[82SC]

to those who use the venerable MFI setup...

do you get strong fuel smells when driving or at a stoplight?

I plan to use MFI but this is one of my concerns...I know the fuel economy is supposed to be better then carbs, but I've heard many people switching to carbs becasuse the MFI was running rich...

Also what about the guys running big engine displacements like p-thomas...I think your is a 3.5L MFI? does that put out alot of fuel smell in the exhaust?

thanks

MJ

[NYSCAR]

Fuely exhaust comes from running rich. Early MFI cars tend to have other issues as well that can cause a gas smell to enter the cabin. A healthy and properly tuned MFI car should not smell, and should run like a top.

Brad

[304065]

I doubt you would get a strong fuel smell sitting at a stop light or driving unless something were amiss. Even if you've got the system richened out and producing black smoke, that stuff shouldn't be working its way up into the fan and into the cabin.

More likely there's a fuel or exhaust leak somewhere. The MFI system (like later fuel injection) uses a "return-style" fuel system that circulates gas out of the tank, through rubber lines over the steering box and into the tunnel, through steel lines in the tunnel and out through a rubber gasket at the rear firewall (under the panel that covers the shift coupler) and then to rubber lines up to the pump at port rear of the car, then out through some more rubber lines to steel lines that run into the engine compartment, then up to the fuel filter console, over to the pump, back to the console and then all the way back to the tank!

In this long trip there's the posibility of a leak, particularly where the fuel lines enter the tunnel (possibility of chafing on throttle linkage) or exit (possibility that rubber grommet has deteriorated and hole has worn in the steel line (also a VW problem)), or even more likely, a bad seal on the fuel tank level sender up front, causing fuel to slosh around in the corners.

Just like NYSCAR said, if everything's right, there should be no smells, even if you have removed the factory charcoal canister, vent system and lines.

As far as switching to carbs because one can't get the MFI to run properly, that's like throwing away a gun because it's out of bullets. Properly tuned the MFI system will produce more horsepower than carbs AND give you better fuel economy, with 98% of the throttle response. It's definitely worth it, but if you are considering converting your 3.0 liter SC motor to MFI, you should investigate extensively the pricing and availability of the 3-dimensional "Space Cam" used in the MFI pump. Presumably you will upgrade to hotter cams in the conversion (another advantage of MFI is its tolerance for radical grinds) and will need a Space Cam calibrated to the increased fuel requirements of such a setup.

[warment]

Sounds like you are indeed running rich. Also, I would check your gas cap seal. Mine was falling apart, so I replaced it. Seemed to help a little bit. I ripped out the charcoal filter and lines and "vented" the gas tank with a fresh piece of hose. This helped too.

Bill